Reactions of o-quinone methides with pyridinium methylides: a diastereoselective synthesis of 1,2-dihydronaphtho[2,1-b]furans and 2,3-dihydrobenzofurans.

A simple, general route to the 1,2-dihydronaphtho[2,1-b]furans and 2,3-dihydrobenzofurans substituted at C-2 by an acyl or aryl group, starting from phenolic Mannich bases and pyridinium ylides, has been developed. The mechanism of the reaction is believed to involve the formation of the o-quinone methide intermediate, Michael-type addition of the ylide to the o-quinone methide, followed by intramolecular nucleophilic substitution.